Mission to the magnetosphere:

Satellite quartet to decode mysteries of space weather

Artist's concept of the a Fregat upper stage with two Cluster II satellites

From staff reports

March 7, 2000
Web posted at: 4:30 p.m. EST (2130 GMT)

(CNN) -- The magnetosphere protects life on Earth from countless billions of charged solar particles blasted continuously from the sun. That much we know, but there are plenty of questions about the planet's natural barrier still to be answered.

To that end, European Space Agency plans to send a flotilla of identical satellites skimming in formation through the magnetosphere this summer. The quartet will collect data and map Earth's magnetic field, providing a critical tool in the relatively young field of space weather forecasting.

Though the magnetosphere normally acts as a shield against the solar wind, it can be breached by high-energy particles (mainly protons and electrons) during periods of increased solar activity.

"It's like a never-ending football game," Cluster II project scientist Philippe Escoubet said in a statement. "The sun is kicking particles toward us, like footballs. The Earth is the goal, and its magnetic field is the goalkeeper."

When particles score goals, they disrupt the Earth, producing electrical currents that can shut down power grids, interrupt
short-wave radio communications or damage communication satellites.

Cluster II is scheduled for launch this June and July, just in time for the Solar Maximum, a peak in the 11-year cycle of solar activity.

The four robotic satellites, each about the size of a Volkswagen Beetle, will be lofted into orbit in pairs by two Soyuz rockets fired from the Baikonur cosmodrome in Kazakhstan.

One of the Cluster II satellites is lifted from a stand during assembly in this file photo

Each satellite is identical in design and carries the same payload: 11 instruments designed to study all aspects of the Earth's electrical and magnetic environment.

The probes' most striking visual features are the booms that extend into surrounding space, sweeping through a sea of charged particles as each spacecraft rotates.

The quartet will fly as a group, collecting data simultaneously while circling the Earth in an oblong orbital trajectory.

"The spacecraft will give us four viewpoints -- like having one camera behind the game at a football match and three others at different angles," Escoubet said. "It will be the first time this has been done in the Earth's magnetic field."

If successful, the mission will mark the first time ESA has built spacecraft in series production and operated them as a single group.

The mission is a duplicate of the original Cluster project, lost during the explosion of the Ariane-5 demonstration flight in June 1996. Cluster II uses some of the original spare parts from Cluster I, and its scientific objectives remain unchanged, according to ESA.

Over their two-year mission, the spacecraft will sail through the various layers and boundaries within the magnetosphere and cross over the edge of Earth's magnetic bubble into interplanetary space, where the solar wind blows full force.

Scientist hope to use the data to create the first detailed,
three-dimensional map of the magnetosphere, which would be an invaluable tool for understanding and predicting the effects of space weather.